text: In the ECW model, a new term W was added to the equation.
  The W term represents a constant energy for cleavage of a dimeric acid or base.  For example, the enthalpy of cleavage the [[rhodium carbonyl chloride|[Rh(CO)Cl]]] by base B involves two steps.  The first step is cleavage of the dimer, which is W:
  :  [Rh(CO)Cl] → Rh(CO)Cl  W = −10.39 kcal/mol
  The second step is the binding of B to RhCl(CO) monomer.  In this case, W = −10.39 kcal/mol.
  In other cases, W is the enthalpy needed to cleave the internal hydrogen bonding of the H-bonding acid (CF)COH.  W is also useful for a base displacement reaction in poorly solvating media:
  : FB-OEt → BF + OEt
  For any base, a constant energy contribution is observed for the breaking of the FB-OEt bond.  An ECW study of the enthalpies of a series of bases produces a W value that corresponds to the enthalpy of dissociation of the FB-OEt bond.  The E and C parameters that result are those for uncomplexed BF.